Toolmaker&#39;s parallel screw clamp



Jan. 8, 1952 H. w. SPRING 7 TOOLMAKERS PARALLEL SCREW CLAMP Filed Dec. 6, 1947 INVENTOR.

HFIRRY W SPRING H-TTORNEY Patented Jan. 8, 1952 UNITED STATES PATENT OFFICE- q I 2,581,978 a I.

' rooLMA mit's- PARALLEL SCREW CLAMP Harry" W. Spring, Waterbury, Conn. Application December 6, 1947, Serial No. 790,036

with a tool working upon said work piece.

Another object is to provide a device of the above nature in which the jaws have portions of different thicknesses in a longitudinally stepped formation so that a single clamp is adapted to hold work pieces of different thicknesses efficiently.

Another object is to provide a device of the above nature which includes a tension screw for controlling the spacing of the jaws, and an outwardly disposed compression screw for holding the jaws in parallel relation.

A further object is to provide a device of the above nature which will be simple in construction, inexpensive to manufacture, easy to manipulate, compact, ornamental in appearance, and very eflicient and durable in use.

With these and other objects in view, there has been illustrated on the accompanying drawing one form in which the invention may conveniently be embodied in practice.

In the drawings,

Fig. 1 is a plan view of the improved tool makerss clamp and a work piece held therein.

Fig. 2 is a side view of the same, showing a working tool and a screw operating pin in broken lines.

Referring now to the drawings in which like reference numerals denote corresponding parts throughout the several views, the numerals I and II indicate a pair of jaws clamped by a compression screw I2, and a tension screw I3 to hold a cylindrical work piece I4. The respective jaws II], II include rectangular base portions I5, l6, and outwardly-extending arms II, I8, which have parallel inner clamping faces I9 20, and outer tapered faces 2 I, 22.

The upper surface of thearm I! of the jaw I0 is formed as a series of steps 23, 24, 25 so that said arm I1 is successively reduced in thickness in an outward direction.

The arm I8 is similarly formed with steps 26, 21, 28 in such a fashion that the steps of the respective arms I'I, I8 are coplanar. The clamping face I9 of the jaw I0 is provided with a plurality of angular recesses 29, each of these reeesses being disposed adjacent the center of one of the steps 23, 24, 25 whereby small work pieces may be firmly clamped. The clamping force exerted by the jaws I0 and II is controlled by the tension screw I3 which passes through a plain bore 30 in the jaw II and into a tapped bore 3I in the jaw ID, the jaw being'held under a knurled capstan head 32 of the screw I3. e

In order to retain the tension screw I3 against longitudinal movement in the jaw I I, said screw is provided with an annular groove 33 immediately adjacent the head 32. A notched retainer clip '34 is engaged in said groove 33 and held against the'outer face of the base-portion I6 of the jaw II by means of a screw 35 secured in a tapped hole 36 in the base portion I 6.

The compression screw I2 is entered through a tapped bore 31 in the base portion I5 of the jaw I0 and is provided with a reduced end bearing 38 which is received in a bearing aperture 39 in the inner face 20 of the jaw II. The screwI2 further has a capstan head 40 which is identical tothehead32 of the screw I3.

Operation In operation, the clamping jaws I0 and II will be separated to the extent necessary for the insertion of the work piece by rotating the screws I2, and I3. An operating pin 4| indicated by broken lines in Fig. 2, may be employed to provide greater leverage in the manipulation of the screw heads 32 and 40. It will be noted that a receding movement of the parallel jaws III and II will be obtained by rotating the screws in the same direction. The work piece I4 will then be inserted between the clamping arms I! and I8 in position to be clamped in one of the angular recesses 29.

In determining the proper recess 29 to receive the work piece, the thickness of the work piece will be taken into account. Thus, when the work piece I4 is inserted with its lower side in flush relation with the bottom surface of the jaws I1 and I8, so as to receive support from a table 43 upon which the clamp is placed, its upper side will project sufficiently above the adjacent stepped sections to permit the unobstructed application of a working tool such as a grinding wheel 42.

In the instance shown in the drawing, the work piece I4 is clamped between the stepped sections 25 and 28, whereby a limited grinding operation may be performed by the longitudinally disposed wheel 42. If the wheel is to be applied in a lateral direction, as indicated by the lines 4211, the extent of the grinding operation will be limited only by the thickness of the stepped sections 25, 28.

Further, if a, work piece of greater thickness is to be held in the clamp, it will be preferable to insert said work piece between the stepped sections 24, 21 or 23, 26 whereby the clamp will engage the work-piece more firmly.

After the work piece has been properly located between the clamping arms I1, I8, the screws 12 and I3 will be rotated to close the arms thereon.

In order to secure the maximum clamping force,

the pin 4! may be inserted in the capstan heads:

32, 4B and used to tighten the screws. The clamp will now hold the work piece'firmly so that it may be operated upon by a tool. p.

One advantage of this invention is that the necessity for keeping a number of clamps of different thicknesses will be avoided, inasmuch as the improved tool makers clamp will serve to efliciently grip work pieces of different thicknesses.

Another advantage is that therelative position of the parallel jaws may be controlledvb'y the tension screw. Thus, if the compression screw I2 is backed off sufiiciently to enable free operation of the tension screw I3, further operation of the screw I2 will be unnecessary until the jaws are in their final position, whereupon the compression screw I2 may be tightened in order to firmlyclamp the work.

While there has been disclosed in this specification one form in which the invention may conveniently be embodied, it is to be understood that this form is shown for' the purpose of illusf tration only, and that the invention is not to be limited to the specific disclosures, but may be modified and embodied in'various other forms,

without departing from its spirit. In short,rthe

invention includes all the modifications and em-,-

bodimentscoming within the scope of the followmg claim. V

Having thus fully described the invention, what is claimed as new, and for which it is desired to secure Letters Patent, is:

In a toolmakers clamp, a pair of parallel jaws comprising coplanar bases adapted to rest fiat upon a table or bench, said jaws having opposing straight inner faces and stepped upper surfaces of successively smaller height to permit the work held between said jaws: to be insertedbelow a grinding wheel and lie ina small vertical space, the inner side face of one of said jaws having work-engaging angular recesses, and a pair of parallel headed screws extending at right angles to said jaws and located within aligned pairs of cylindrical holes, one of each of said pairs of holes being tapped, each of said screws being in threaded engagement with a tapped hole and Number Name Date 2 269,5l46 Moss Dec. 19, 1882 876,908 Ljunglof Jan.14,- 1908 71,286,314 Hertle Dec. 3, 1 918 1,370,994 Pomerenke' Mari-8,1921

1,855,94 Delacour f Apr. 26,1932 2,441,743 Albert "May18,'1948 

